As long as you have a Wi-Fi connection that supports network access to the RIM data centre your BIS is supported on all your RIM applications, including BBM, will use Wi-Fi. You will know that BIS is connecting using Wi-Fi when on the top right hand corner of your home screen the BlackBerry logo is next to the Wi-Fi signal strength icon. When this is not the case, and you have a Wi-Fi connection there is a network issue between the Wi-Fi access point and the RIM data centre.